Heat treating furnace



March 15, 1932. C HAYES 1,849,714 l HEAT TREATING FURNACE Filed Aug.28', 1950 2 Sheets-Sheet l t j ff' UA a a *n T www Mum

ATTORNEYS.

March 15, 1932. C. l. HAYES HEAT TREATING FURNACE Filed Aug. 28, 1930 2Sheets-Sheet 2 IN VEN TOR. @df/[Hayle .9 Bm

ATTORNEYS.

Patented Mar. 1'5, 1932- -PATENT OFFICE CARLI. HAYES, OF PROVIDENCE,IFHODE ISLAND HEAT TRELATING FURNACE Application iiled August 28, `1930.Serial No. 478,334.

My present invention relates to improve-- l ments in heat treatingfurnaces, and has particular reference to improvements for maintaining aconstant gaseous atmosphere of des sired constituency within the heattreating chamber.

A serious difficulty confronted during a heat treatment results from thechanging atmospheric conditions within the heat treating 1o chamber whenopening the door thereof to insert material in or to remove materialfrom the chamber. lVhle one method of obviating this diiiculty is tomaintain an open mouth for the heat treating chamber, this methodrequires a much greater flow of gases to form an air excluding curtainthan is necessary with a door closure; if suiicient -gas How ismaintained to produce the desired treating atmosphere with the doorclosed, the outside air will penetrate through the protecting curtainwhen the door is opened and adversely affect the gaseous atmosphere inthe heat treating chamber. One object of my invention is to reduce theamount of curtain gases necessary for adequate protection, and at thesame time compensate for the door opening by regulating the gas flow sothat an adequate curtain is'provided with the door closed, and thenproviding an additional gas flow to reinforce the curtain gases andensure adequate exclusion of the outside air when the door is open.Thisadditional flow is preferably automatically controlled in accordancewith the amount of door opening, so that the atmospheric conditionswithin the heat treating chamber remain constant regardless of theposition of the door.

A further object of my invention is to shape the throat of the furnaceso as to assist in the formation of a proper curtain, and to direct thegas flow to throw the upwardly flowing curtain gases forwardly towardsthe entrance to the heat treating chamber, thus further assisting intheformation of the curtain.`

lVith these and other objects and advantageous features in View, theinvention `con sistsin a novel method and a novel arrangement of lpartsmore fully disclosed in the detailed description following,.inconjunction With the accompanying drawings, and more particularly setforth in the appended claims.

In the drawings: Fig. 1 is a front View of the improved heat treatmentfurnace, the doors being shown in 5.5

closed position;

Fig. 2 is a central vertical section through the heat treating furnaceon the line 2-2 of Figure 1;

Fig. 3'is a vertical section on the line 3 3 of Figure 2;

Fig. 4 is a horizontal section on the line 4-4 of Figure 2;

Fig. 5 is a view of a modified valve control for permitting independentmanual control of the valves Whenever desired.

It has been found desirable in constructing heat treatment furnaces,particularly furnaces of the electric type, to provide a protectivegaseous curtain for the throat of the heat treating chamber, and to soregulate this gaseous curtain that it will maintain the desiredatmospheric conditions Within the heat treating chamber irrespective ofthe position of the furnace door. This regulation is preferably obtainedby permitting a regulated flow lof gases to form a curtain suitable forprotection when the door is closed, and to provide an additional flow ofgases to reinforce the curtain when the door is open; in addition, thethroat is shaped to diverge to- Wards the entrance. opening and the gasflow is directed towards the entrance opening, in order to facilitateexclusion of the atmospheric air; and the following is a detailed 85description of. a preferred construction which embodies the principlesof my invention.

Referring to the drawings, the heat treatment furnace 10 is of standardconstruction, Y 90 and is preferably mounted on vertical standards 11 inorder to position the furnace opening at the proper height for easilyinserting and removing articles to be treated. Within the heat treatmentfurnace is a heat treat- 95 ing chamber 12, having the usualthroat 13the entrance to which is normally closed by the vertically movable door14 supported in the usual manner by cables 15 mountedon pulleys 16 andcounterbalanced by a Weight 100 or weights 17. The door 14 is preferablyequipped with a peep-hole opening 18 which may have a closure shield, ifdesired, for permitting the operator to glance into the heat .treatingchamber and observe the condition of the work therein. The chamber 12may be heated in any desirable manner. but preferably is equipped withresistance bars 19 for receiving aheating current, thus heating the workby radiation. A trough or channel member 20 is provided in the heatingchamber and is mounted on suitable supports21 and ledges 22, to receivethe work to be heat treated. Y

Referring now to Figure 2. a combustion chamber 23 is positioned belowthe throat- 13, and communicates with the throat through a verticalnozzle slot 24, which as shown in Figure 2 is parallel to the throatentrance and is forwardly directed so as to throw the gases from thecombustion chamber 23 against the upper wall of the throat 13. Thecombustion chamber 23 receives combustible gases and oxygen bearinggases through conduits 25 and 25 respectively, these conduits preferablybeing positioned outside the furnace and communicating with thecombustion chamber 23 through any suitable nozzle Varrangement or thelike 26. The conduits 25 and 25 each have a by-pass line, designatedrespectively 27, 28, both the by-pass lineand the main flow line foreach conduit being provided with manually controlled valves, 29, 30, 31and 32. two main cut-olf valves also being provided for each conduit.The conduits have further controls in that two additional valves 33, 34are provided. preferably of the rotary type, adapted to be actuated bylinks 35, 36 which are connected at their ends by a link 37, the linkageas a unit being actuated by reciprocating movement of a vertical rod 38which is hingedly connected to an arm 39 mounted on the pulley shaft 40,wherebv rotation of the pulleys bv the usual manually .operated lever40a to lift the door 14 also shifts the rod 38 and thus opens the valves33 and 34 to automatically increase the supply of combustible gases andoxygen bearing gases in direct proportion to the door opening.

The described arrangement operates as follows: The hand controlledvalves 30. 32 are set to feed the desired proportions of air and gas tothe combustion chamber` the door being in closed position. The valves29. 31 are set to supply the door-controlled valves 32. 34 with theproper proportions of air and gas so as to maintain the desiredatmospheric conditions in `the furnace regardless of the eg'rtent ofopening of the door, it being desirable in the case of furnaces havingrelatively large door openings and therefore substantial exposure to theatmospheric oxygen, to set the valves 29 and 31 soas to feed an excessof gas.

The rate of the gas flow in the conduits 25 and 25 may be visuallyobserved by means of manometers 41, 42 mounted on the furnace andrespectively connected to flow indicators 43, 44 positioned in therespective flow conduits.

Referring now to Figures 2 and 4, it will be noted that the throat 13 ispreferably provided with walls diverging towards the entrance, thusassisting in throwing the curtain gases forwardly, this action beingfurther assisted by the forward slant of the nozzle slot 24.

It may be preferable under unusual operating circumstances, -to providefor hand control of the auxiliary valves 33 and 34. This is preferablyaccomplished by forming the end of the rod 38. as shown in Figure with avertical slot 45 therein and a transverse slot 4G centrally positionedwith respect tothe slot 45 and communica-ting therewith for receivingthe pin 47 which connects the vertical link 37 with the upper valve link35. The rod 38 is spring held by means of a coil spring 49 or the likeso as to normally lock the pin 47 within the opening 46. If manualcontrol of the valve 33 and 34 is desired, the rod 38 is swungforwardly, and the handle 48 of the link 3? is swung so as to bring thepin 47 out of the slot 46 and into the slot 45, whereupon the valves 33and 34 may be shifted by movement of the handle 48 inde* pendently ofthe position of the door 14.

This control of the flow of gases into the combustion chamber 23 issuit-able for maintaining the operating conditions in the heat treatingchamber which are most desirable for the work under heat treatment.Thus, in the heat treatment of certain classes of jewelry, it ispreferred to use hydrogen as the atmospheric medium; in this case. theadjustment of the valves 30 and 32 provides the minimum flow of hydrogennecessary to form a protective curtain when the closure member 14 is indown position; as the member 14 is lifted, the access of the outside airrequires a greater iow of hydrogen, which is obtained by movement of thecontrol valves 33 and 34 in exact accordance with the lifting of thedoor.

When a constant neutral gas atmosphere is desired in the heat treatingchamber, the valves 29 and 32 are adjusted so as to obtain perfectcombustion within the combustion chamber 23. The valves 33 and 34 arethen adjusted in the same proportion, and serve to increase the amountof gases as the closure member lifts to still maintain the proper ratiobetween the two `gases for complete combustion.

lVhen heat treating high speed steels, a slight reducing atmosphere isfound most desirable. ln such case, the valves 30 and 32 are adjusted soas to obtain a slight excess of CO in the curtain gases, and the valves29 and 31 are also adjusted so that as the closure member is raised, theadditional flow of gases into the combustion chamber will alwaysmaintain 4the same suitable amount of excess CO in the heat treatmentchamber 12, the adjustment providing enough excess CO to preventpenetration of the atmospheric oxygen through the curtain.

While I have `described a preferred construction of furnace, it isobvious that desired changes in furnace construction, in the number ofopenings, in the relative volumes and relationship of the various parts,and in the type of controls used, may be made to suit the requirementsof particular heat treatment installations, Without departing from thespirit and scope of the invention as defined in the appended claims.

I claim:

1. :In the art of heat treatment, the method of controlling the heattreatment of material in a heat treat-ing chamber having an opening anda movable closure member for said opening, comprising supplying agaseous medium to said chamber to obtain a desired gaseous atmospheretherein, and increasing the supply of the gaseous medium to compensatefor movement of said closure member '.to open positlon. v

2. In the art of heat treatment, the method of controlling the heattreatment of material 1n a heat'treating chamber having an opening and amovable closure member for said openlng, comprising supplying a gaseousmedium to said chamber to obtain a desired gaseous atmosphere thereinand to form an air-excluding'curtain for said opening, and increasingthe supply of the gaseous medium to compensate for movement of saidclosure member to open position.

3. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening, means for supplyinga gaseous medium of predetermined constituency to said chamber, andmeans operating in accordance with movement of said closure member tomaintain the same constituency of the gaseous medium in said chamberWhether said closure member is in open or shut position.

4. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening, means forproj|ecting a. gaseous medium across said opening to form anair-excluding curtain therefor and to produce an atmosphere of saidgaseousv medium in said chamber, and means operating in accordance withmovement of said closure member to maintain the same constituency of theatmosphere in said chamber whether said closure member 'is in open orshut position.'4

5. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening, means for -supplyinga non-oxidizing gaseous medium to said chamber, and means forautomatically changing the supplyof gaseous medium in accordance withchange in position of said closure member.

6. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening, means for projectinga non-oxidizing gaseous medium across said opening to form anair-excluding curtain therefor and to produce an atmosphere of saidgaseous medium in said chamber, and means for automatically changing thesupply of gaseous medium in accordance lvith change in position of saidclosure mem- 7. In a heat treatment furnace, a heat treating chamberhaving an opening, a movable closure member for said opening, means forsupplying combusted gases to sald chamber to form a Work envelopingatmosphere, and

means operating in 'accordance with movement of the closure member formaintaining the same atmospheric constituency in said chamber when saidclosure member is in open or shut position.

8. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening, means for.projecting combusted gases-across said opening to form an air-excludingcurtain therefor and to produce an atmosphere of said gaseous medium insaid chamber, and means operating in accordance with movement of theclosure member for maintaining the same atmospheric constituency in saidchamber when said closure member is in open or shut position.

9. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening, means for supplyingcombusted gases to said chamber to form a Work enveloping atmosphere,and means operating in accordance with movement of the closure memberfor increasing the supply of gaseous medium upon opening of said closuremember.

l0. In a heat treatment furnace, a heato eninO' to form an air-excludinocurtain therefor and to produce an atmosphere of said gaseous medium insaid chamber, and means operating in accordance with movement of theclosure member for increasing the supply of gaseous medium upon openingof said closure member. y

11. In a heat treatment furnace, a heat treating chamber, a throatleading to said chamber, a closure member for the throat entrance, anozzle slot in the bottom wall of said throat, a combustion chambercommunieating with said nozzle slot, conduits for supplying combustibleand combustion supporting material to said combustion chamber, and meansoperating in accordance with movement of the closure member forincreasing the supply of said material upon movement of said closuremember to open position.

12. In a heat treatment furnace, a heat treating chamber, a throatleading to said chamber, a closure member for the throat entrance, thecross-sectional area of said throat increasing toward the throatentrance, a nozzle slot in the bottom wall of said throat, a combustionchamber communicating with said nozzle slot, and conduits for supplyingcombustible and combustion supporting fluid to said combustion chamber.

13. In a heat treatment furnace, a heat treating chamber. a throatleading to said chamber. a closure member for the throat entrance. thewalls of said throat converging towards the throat entrance, a nozzleslot in the bottom wall of said throat, a colnbustion chambercommunicating with said nozzle slot. conduits for supplying combustibleand combustion supporting gas to said combustion chamber, and meansoperating in accordance with movement of the closure member forincreasing the supply of said gas upon movement of said closure memberto open position.

14. In a heat treatment furnace, a heat treating chamber, a throatleading to said chamber, a closure member for the throat entrance, anozzle slot in the bottom Wall of said throat positioned to direct gasesissuing therefrom forwardly towards the throat entrance. a combustionchamber communicating with said nozzle slot, and conduits for supplvingcombustible and combustion supporting gas to said combustion chamber.

15. In a heat treatment furnace, a heat treating chamber, a throatleading to said chamber. a closure member for the throat entrance, thecross-sectional area of' said throat increasing toward the throatentrance, a nozzle slot in the bottom wall of said throat positioned todirect gases issuing therefrom forwardlv towards the throat entrance, acombustion chamber communicating with said nozzle slot. conduits forsupplying combustible and combustion supporting gas to said combustionchamber, and means for increasing the supply of said gas upon move? nrntof said closure member to open position.

16. In a heat treatment furnace, a Aheat treating' chamber` a throatleading to said chamber. a closure member for the throat entrance. thewalls of said throat converging towards the throat entrance, a nozzleslot in thc bottom wall of said 'throat positioned to direct gasesissuing therefrom forwardly t0- wards the throat entrance, a combustionchamber communicating with said nozzle slot. -means for supplyingcombustible and combustion supporting material to said combustionchamber, and means for increasing the supply of said material uponmovement of said closure member to open position.

17. In the art of heat treatment, the method of controlling the heattreatment of material in a heat treating chamber having an opening and amovable closure member for said opening, comprising supplying productsof combustion to said chamber to obtain a gaseous atmosphere -ofpredetermined constituency therein, and increasing said supply ofproducts of combustion to compensate for movement of said closure memberto open position, whereby an identical gaseous atmosphere is maintainedin said chamber whether said closure member is in open or shut position.

18. In the art of heat treatment, the method of controlling the heattreat-ment of material in a heat treating chamber having an opening anda movable closure member for said opening, comprising supplying productsof combustion to said chamber to obtain a gaseous atmosphere ofpredetermined constituency therein and to form an air-excluding curtainfor said opening, and increasing said supply of products of combustionto compensate for movement of said closure member to open position,whereby an identical gaseous atmosphere is maintained in said chamberWhether said closure member is in open or shut position.

19. In a heat treatment furnace, a heat treating chamber having anopening, a closure member for said opening, a combustion chamber, meansyfor supplying combusted gases from said combustion chamber to said heattreating chamber, means for supplying a regulated amount of combustiblegas and of air to said combustion chamber sufficient to excludeatmospheric air when said closure member is in closed position, andmeans for supplying a further regulated amount of combustible gas and ofair to said combustion chamber to compensate for movement of saidclosure member to open position, whereby an identical gaseous atmosphereis maintained in said chamber whether said closure member is in open orclosed position.

2'0. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening` a combustionchamber, means for projecting combusted gases from said combustionchamber across said opening to form an atmosphere excluding curtain,means for supplying a regulated amount of combustible gas and of air tosaid combustion chamber sufficient to form said atmosphere excludingcurtain when said closure member is in closed position, and means lforsupplying a further regulated amount of combustible gas and air to saidcombustion chamber sufficient to maintain said atmosphere excludingcurtain to compensate for movement of said closure member to openposition.

21. In a heat treatment furnace, a heat treating chamber having anopening, a movable closure member for said opening, a combustionchamber, means for projecting combusted gases from said combustionchamber across said opening to form an atmosphere excluding curtain,conduits for supplying combustible gas and air to said combustionchamber, valves in said conduits, by-pass conduits by-passing saidvalves, additional valves in said by-pass conduits and mechanismcontrolling said additional valves and operable to increase the supplyof gas and air to said combustion chamber upon movement of said closuremember to open position.

In testimony whereof I affix my signature.

CARL I. HAYES.

